JP5990101B2 - Molded products for automotive panels - Google Patents

Description

  The present invention relates to a molded product and a manufacturing method thereof.

  In the automotive industry, structural panels are used in a wide range of applications where high strength and light weight are required. Molded reinforced panels are used especially in motor vehicles, for example as parcel shelves, ceilings, engine bay panels or road floors, as well as panels used outside the vehicle, such as engine undershields or external wheel arch liners . Additional acoustic properties for noise attenuation, particularly the material's sound absorption coefficient, may be a requirement. For example, composite panels that ultimately have a honeycomb core are used in trim parts, sunroof panels, hardtops, parcel shelves, covers for spare wheels, and cargo bed floor assemblies. Depending on the material selected, they may also be used as an underfloor, engine cover or engine bay cover. Fiber reinforced composites are used as a main material or as a skin layer for their products, sometimes in combination with additional layers for specific purposes.

  A composite material (or composite for short) is an engineering material that is manufactured from two or more components that have significantly different physical or chemical properties, said components being in the finished structure It remains separated and distinguished at a microscopic level.

  Composites are made up of individual materials referred to as constituent materials. There are two categories of constituent materials: matrix materials and reinforcements. At least a portion of each type is required. The matrix material surrounds and supports the reinforcing materials while maintaining their relative positions. The reinforcement imparts special mechanical and physical properties and enhances matrix properties. Synergistic action creates material properties that are not available from individual components. Engineering composites must be shaped. The matrix material can be introduced into the reinforcement before or after the reinforcement material is placed in the mold cavity or on the mold surface. The matrix material undergoes a change in physical state, such as a melting event for a thermoplastic material, after which the shape of the part is essentially fixed. Depending on the nature of the matrix material, this change in the physical state can variously result in, for example, chemical polymerization (thermosetting) or solidification from the molten state (thermoplasticity).

  Most commercially produced composites use polymer matrix materials often referred to as resin solutions. There are many different polymers available depending on the starting material components. There are several broad categories, each with numerous variations. The most common are known as polyester, vinyl ester, epoxy, phenol, polyimide, polyamide, polypropylene, PEEK and others. The reinforcing material is often a fiber, but is usually also a ground mineral. A composite material can be produced by using a layer or mat of fibrous material at least partially composed of reinforcing fibers, such as glass fibers and binder material (either in powder, liquid solution or binder fiber form). . The materials are mixed and usually cured by thermoforming in a molding press to produce the desired product shape directly.

  US20050214465 discloses a method of manufacturing a composite using polyamide as a matrix, wherein the reinforcing material is impregnated with a lactam melt activated for anionic polymerization and then heated. Yes. Another known method is a pultrusion method. The material to be produced can be ground and then used in injection molding or extrusion processes.

  Another technique used is the mixing of reinforcing fibers and thermoplastic melts. Here again, mainly the injection molding continues and finally the compression molding follows to obtain the desired form of the product.

  The use of thermoplastic melts or impregnation with melts makes the resulting product compact and nonporous. This is because the melt fills the space between the reinforcing materials and plugs all the existing pores.

  US71332025 discloses a method of using thermoplastic fibers as matrix material. The fibers are first compounded with reinforcing fibers and then dried to provide a compounded web. The web is then consolidated by needling, heated and densified to yield the final product. The web is heated to a temperature above the softening point of the thermoplastic fibers using a conventional oven or by IR irradiation and directly compressed, compressed and partially consolidated thermoformable Semi-finished products are provided.

US20050140059 is a method of manufacturing a molded part made of fiber, in which the fiber is first heated between plates and then subjected to compression molding, additionally using air suction to produce a better shaped product A method is disclosed. The fibers used are bicomponent fibers as binder fibers and other fibers as bulk fibers, such as reprocessed cotton and polypropylene. Even though the introduction mentions the use of high pressure steam or flowing air as an alternative to heating the material prior to compression molding, the actually disclosed method only uses a heating plate and is Heat to 1 minute to make and integrate the fiber material. The use of steam is not disclosed in combination with the materials used and the disclosed method.

  WO2004098879 discloses a method for producing a composite material of a mixture of thermoplastic fibers and reinforcing fibers using a needled nonwoven as starting material. This web is combined with a double foil having a high melt thermoplastic material and a lower melt thermoplastic material. The layered laminate is then long enough to allow softening to the temperature at which the thermoplastic fibers and low melt thermoplastic material of the foil are heated above their melting temperature using infrared or hot air. It is heated in a short time. Immediately thereafter, the layered material is pressed, for example using a roller. As an example, this patent discloses a combination of polyamide-6 as a binder fiber and glass and PET fibers as reinforcing fibers.

  WO2007000225 also discloses a manufacturing method of a hard part using a combination of a low melting fiber and a high melting fiber, in which the fiber web is heated above the melting temperature of the low melting fiber. The application further discloses the use of glass or polyester fibers as high melt fibers and polypropylene or polyester as low melt fibers in the core material. This core material is layered between two outer thermoplastic foil layers. During the heating phase, the inner core material spreads due to internal pressure within the core fibers, resulting in a lofting effect throughout the material. The final product includes a partially highly compressed area and partially this raised area. In practice, this is done using a combination of polypropylene and glass fiber and is referred to as soft lofting.

  The disadvantage of the prior art is that high temperatures are required to obtain the final composite. The heating temperature to be achieved depends on the matrix polymer. To form the composite, the matrix and reinforcing fibers are heated using a dry heating method such as hot air, contact heating or infrared heating. The product is usually heated above the actual melting point of the matrix polymer to compensate for temperature loss from, for example, device heating to device molding. Heating the polymer above its melting point promotes decomposition.

  The use of a contact heater has the further disadvantage that the product must be compressed in order to transfer heat well throughout the thickness of the product. Hot air is usually used at temperatures above the melting temperature of the binder polymer, so that the polymer is thermally damaged, while the use of infrared heating is only possible for thin materials. For thicker materials, the amount of energy required to heat the inner core damages the outer surface polymer. This method is usually only used for thicknesses up to 4-5 mm.

  Another drawback is that most thermoplastic polymers used as matrix fibers and as reinforcing fibers have melting temperatures close to each other, for example polyethylene terephthalate (PET) has a melting temperature of 230-260 ° C. The range is between 140 and 170 ° C for polypropylene, between 170 and 225 ° C for polyamide-6 and between 220 and 260 ° C for polyamide-6.6. Heating them above the melting temperature of the matrix fibers using matrix fibers and reinforcing fibers, both of which are thermoplastic polymers, for example PA 6.6 as a matrix and PET as a reinforcing material, will cause melting or softening of the reinforcing fibers Also causes the start of. This leads to a collapse of the structure and forms a very dense composite.

  The felts are widely used for their thermal insulation and sound insulation properties, especially in the automotive industry. The trend is towards renewable materials, so thermoplastic binders have occupied a significant share in recent years. Fibers made of high performance polymers such as polyester, polyamide are of great interest due to their mechanical and heat resistant properties. However, the required binder is a limitation on their use in molded 3D members.

  The binders used so far always have a lower melting point than the reinforcing fibers, making the molded fiber web a relatively weak performance behavior and limiting its use to the tempered area in the vehicle. None of these types of molded fiber webs are suitable for exposure of engine bays or compartments to high temperatures, particularly in the engine contact area. Some of these binders are modified polymers (by way of example CO-PET) that have a pour behavior because of their modified structure that is particularly sensitive to hydrolysis phenomena.

  Methods for molding such felts known in the prior art are “cold” molding methods, in which the felt is preheated by various means and then transferred to a cold mold and compressed therein to obtain the part shape. Is a “hot” molding process in which is introduced into a closed mold and a heat transfer medium, such as air, is introduced therein to bring the binder to its melting point and then released. Thereafter, the part is cooled inside or outside the tool with or without the aid of cooling. (See, for example, EP 1656243, EP 1414440, and EP 590112).

  The object of the present invention is therefore to find an alternative method for combining matrix and reinforcing fibers without the drawbacks of the current technology, and can be used in automotive applications, especially in engine bays or other areas with high temperatures. To get a product.

Comprising at least one polyamide reinforcing layer consisting of a polyamide matrix and reinforcing fibers, the polyamide reinforcing layer due to the integration of the matrix material and reinforcing fibers in fiber or powder or flake form using a pressurized steam process Steam for integrating the polyamide product applied in powder, flake or fiber form with the composite product of claim 1 and as a matrix, characterized by being porous, and reinforcing fibers Using the method of claim 8 using a process, it is possible to contain a lofty web structure of reinforcing fibers, resulting in a porous reinforced material. This material has good dynamic Young's modulus and is thermally stable.

  Lofted air permeable composite with increased hardness of randomly placed binding fibers and reinforcing fibers bonded at overlapping positions by thermoplastic resin spheres of the bonding fibers A method of manufacturing was developed.

In this method, high elastic reinforcing fibers are mixed with matrix-forming polyamide fibers, or polyamide powder or flakes, to form a web by any suitable method such as air laying, wet laying, carding and the like. The web is then heated using saturated steam to melt the resin matrix material at a temperature below that of the polymer as measured using differential scanning calorimetry (DSC) according to ISO 11357-3. For example, the melting temperature T _m of polyamide-6 (PA-6), measured using DSC, is 220 ° C. However, the melting temperature of the same PA-6 in the steam process according to the invention is, for example, 190 ° C.

  The web is placed in a pressure resistant mold having at least one vapor permeable surface. The mold is closed and tightened to withstand the internal pressure. Saturated steam with an absolute pressure of at least 9 bar is applied to melt the binder. Saturated steam higher than 20 bar absolute pressure is no longer economical. Preferably, a range of 11-15 bar absolute pressure is a good working range. The actual shift in the melting temperature of the polyamide depends on the vapor pressure generated in the hollow chamber where the product is steam formed. Thus, the choice of pressure used also depends on the melting temperature of the reinforcing fibers. For example, when PA-6 is used as the binder fiber, the preferred pressure is 11 bar absolute pressure to 15 bar absolute pressure.

  By using steam instead of normal hot air, hot plates or IR waves, it is possible to shift the melting point of the polyamide to lower temperatures using the effect of water molecules in the steam. The effect of water on polyamides is known and usually regarded as a drawback, and many prior arts describe ways to avoid or prevent that effect. Surprisingly, PA (polyamide) applied in the form of powder, flakes or fibers and other thermoplastic fibers having a similar melting point measured using DSC, such as PET (polyester), It is exactly this effect that is used as the only bonding material, allowing the reinforcing fibers, eg PET, to be held in their fibrous form and combined. It is now possible to obtain heat-stable molded products that have a porous structure and thereby enhance acoustic properties, such as absorption and airflow resistance, and thermal conductivity.

  The effect of steam is based on a reversible diffusion mechanism. When polyamides in the form of small fiber diameters or particle sizes are used, melting and solidification is rapid and provides a short production cycle. As the vapor is released from the mold, the polyamide changes to a solid state and the part can be demolded as a rigid part. This is advantageous compared to other thermoplastic binders that clearly need to be cooled on the inside or outside of the mold before obtaining a handleable structured part.

  Since the overall temperature used here can be kept much lower compared to heating methods without steam, the elasticity of the PET fibers remains intact and the more lofted material Squeak. Furthermore, it has been found that the PA binding is sufficient to obtain the required hardness of the final product. This is because PET fibers retain their elasticity and PA melt matrix material only bonds the intersections. The material retains its dignified appearance due to the void volume in the web. Therefore, the final product is still air permeable. Furthermore, it has been found that the use of steam is advantageous when glass fibers as reinforcing fibers are used together with polyamide fibers as matrix. Thanks to precise control of the bonding properties, less energy is required for both the heating and cooling steps.

  In a normal heating step, the material is heated to the melting point of the thermoplastic matrix material. The cooling of the material is slow due to slower heat convection outside the product because the material falls together and becomes more dense due to the lack of elasticity of the reinforcing fibers. . Thus, the molten state continues for a longer time. Therefore, it is more difficult to control the amount of coupling. Furthermore, during this cooling time, the material remains flexible and is therefore more difficult to handle due to the longer molten state of the bonding matrix. Especially when dealing with larger automotive trim parts, such as headliners or road floors for trucks or larger vehicles.

  Surprisingly, it was also found that as soon as the vapor was removed from the material, the melting process stopped immediately and the material again obtained its solid state. This is advantageous in the ability to reduce manufacturing cycle time because the material can be handled immediately. The fact that the melting process can be stopped immediately is also a very accurate means of controlling the bonding properties and thus the porosity of the material. That is important for the air permeability of the material.

The material used for the polyamide matrix may be in the form of powder, flakes or fibers. However, the use of fibers in combination with reinforcing fibers is most preferred because the fibers mix better and remain in the mixed position prior to integration while handling the formed web. Because there is a tendency to. Flakes or powder may fall between the reinforcing fibers and off the web or to the bottom of the mold.

  As polyamides, all kinds of polyamides, in particular CoPA (copolyamide), polyamide-6 (PA-6) or polyamide 6.6 (PA6.6) can be used. However, various types of polyamides or mixtures of various types of polyamides also serve as binders according to the invention. Additives commonly used in basic polyamide formulations are expected to be part of the claimed basic polyamide material, for example chemical compounds to obtain UV resistance.

  The reinforcing fiber may be any thermoplastic polymer-based material having a melting temperature as measured by DSC that is higher than the melting temperature of the polyamide binder in the steam environment. PET with a melting temperature of 230-260 ° C. will work well as a reinforcing fiber. The reinforcing fibers may be any mineral material, in particular glass fibers (GF), carbon fibers or basalt fibers. Mixtures of both groups of reinforcing fibers can also be used, for example, PET with GF. Material selection is based on the overall thermal stability requirements of the final product and the price of the individual materials.

  The reinforcing fibers may be cut fibers, endless filaments or rovings depending on the material properties required.

  These and other features of the invention will be apparent from the following description of preferred forms, given by way of non-limiting example, with reference to the accompanying drawings.

Graph of dynamic Young's modulus of various samples Graph of loss factor of the same sample Comparison of sound absorption of webs integrated using thermoformed plates or steam processes according to the present invention Comparison of thermal conductivity of webs integrated using a thermoformed plate or steam process according to the present invention.

For the composite according to the invention, matrix-forming binder fibers are mixed with reinforcing fibers and carded to form a web. The web was pre-bonded using needling for handling. (However, any type of prebonding method may be used.) Use thin nonwoven fabric as a surface cover to prevent the composite sample from sticking or solidifying to the mold, especially when releasing the vapor pressure from the instrument. You can do it. The nonwovens used have a negligible effect on the main characteristics, such as the thickness, acoustic behavior or hardness of the final product. The polyamide reinforcing layer web according to the present invention was integrated using the specified saturated steam.

  Prior art samples were compared with polyamide reinforcing layers according to the present invention. Prior art composites have been available on the market.

Composite 1A Prior art composite based on polypropylene as a binder and glass fiber as a reinforcing material, having a density of 881 kg / m ³ and known in the market as Symalite.

Composite 2A A prior art felt-based material having a density of 314 kg / m ³ and made of bicomponent PET as a binder material and cotton as a reinforcing material.

Composite 3A A composite according to the invention made of 45% PA binder fibers and 55% glass fibers as reinforcing fibers. The starting mass of the web, was m ² per 1000 g. The composite was molded according to the present invention for 9 seconds using 11 bar absolute pressure saturated steam. The final density of the molded polyamide reinforcing layer is 384 kg / m ³ .

Composite 4A A composite according to the invention made of 55% PA binder fiber and 45% glass fiber as reinforcing fiber. The starting mass of the web, was m ² per 1000 g. The composite was molded according to the present invention for 9 seconds using 11 bar absolute pressure saturated steam. The final density of the molded polyamide reinforcing layer is 303 kg / m ³ .

  The dynamic Young's modulus with respect to the temperature range was measured, and the tensile loss coefficient was calculated from this according to ISO 6721-4. Measurements and calculations were performed using a 0.1 dB Metaviv Viscoanalyzer Type VA 2000. See FIGS. 1 and 2 for results on all composites.

  There is an increasing demand for thermal stability for composite parts used in the automotive industry. Especially in the engine bay, directly for new motor generations that generate more heat, as well as for the option of using isolation to keep the heat inside and optimize the overall use of the fuel The demand for higher thermal stability is highlighted. Typically, the test for engine bay materials is a long term thermal stability test at 120 ° C or 150 ° C. However, the actual temperature can easily rise to 180-190 ° C. for a short time. This temperature range may occur on the hot engine side, for example near or around the exhaust line, manifold, or compressor.

  One requirement for thermal stability testing is to know if the composite product will retain its form or shape while exposed to heat. For example, parcel shelves installed under a sunny window should not sag after a while. The engine bay cover must be kept firm. The tensile loss factor over this temperature range is important to maintain the hardness of the product when used.

  FIG. 1 shows the dynamic Young's modulus. Composite 1 Prior art products based on PP matrix and glass fibers as reinforcement show higher modulus than composites 2 and 4 according to the invention in absolute terms. This is mainly due to the higher overall density. However, the tendency is to obtain the same or better hardness performance at lower density and reduce the mass in the car. More importantly, however, the prior art composite 1 exhibits a significant loss of dynamic Young's modulus over the measured temperature range. Therefore, products manufactured in combination with PP tend to be softer at higher temperatures. The composite material 2 is a combination of CoPET / PET bicomponent bonded fibers and cotton as a reinforcing material, and exhibits a dynamic Young's modulus that is too low overall to be self-supporting.

  The composite according to the invention behaves better over the measured temperature range. It has been found that the dynamic Young's modulus of the polyamide reinforced layer does not change more than 20% over a temperature range of 150 ° C to 210 ° C. The product becomes more thermally stable overall.

  FIG. 2 shows the tensile loss factor over the temperature range measured in the composite product. The composite 1 is of the prior art based on polypropylene (PP) as a matrix binder fiber manufactured using a molding method that does not use steam. Even though the product has a good loss factor up to 160 ° C., it rapidly loses thermal stability due to melting.

  The composite material 2 is a combination of CoPET / PET bicomponent bonded fibers and cotton as reinforcing fibers. Thus, the poor loss factor over the measured temperature range is essentially due to CoPET, already softening at 80 ° C. and starting to melt above 110 ° C. However, this depends on the CoPET used. Higher molten CoPET has other disadvantages including increased costs. In an absolute way, a composite material using PET alone may result in a product with good thermal stability, but which does not thermally damage the reinforcing fibers due to the very high melting temperature required. It is not currently known how this can be achieved.

Composites 3 and 4 are a combination of PA binder and glass fiber reinforced fibers integrated using steam according to the present invention. Both have a stable tensile loss factor (−) of less than 0.15 over a temperature range of 60-210 ° C.

The polyamide reinforced product can be fully or partially compressed to obtain a molded product. Thanks to the integration process using saturated steam according to the invention, it is possible to obtain a product with a lower density but still obtaining the desired hardness. Since the heating process using saturated steam melts the polyamide binder fibers at a much lower temperature than the thermoplastic reinforcing fibers and spans the entire thickness almost simultaneously, the elasticity of the reinforcing fiber web structure can be maintained. By reducing the amount of matrix-forming polyamide to a level where the entire product is just fully bonded, a porous reinforcing layer can be obtained at a density that is only 5-80% of the bulk density of the composite material. . However, preferably a range of 5-60%, even more preferably 5-25% is obtained, and more advantages are obtained due to the lower cost of the whole part. It is thus possible to obtain a product that remains porous rather than solid, with a better sound absorber (see FIG. 3) as well as better thermal conductivity (see FIG. 4) due to the porosity of the material. become. By controlling the density either by further tamping or by increasing the amount of PA matrix, it is possible to control both acoustic properties as well as thermal conductivity.

Samples A and B were made using the same web material of 65% glass fiber and 35% PA binder fiber. Composite A was integrated using saturated steam according to the present invention, and Composite B was integrated using compression between hot plates. Both were processed so that full product coupling was achieved.

  The sound absorption characteristics of the molded composite were measured using an impedance tube according to the standards for ASTM (E-1050) and ISO (10534-1 / 2) impedance tube measurements (measurements between 200-3400 Hz). Thermal conductivity was measured according to ISO 8301 using a guarded hot plate.

Sound absorption and thermal conductivity have been found to be better in steam treated products than in hot plate treated products. This is due in part to the need to use additional compression to obtain a fully bonded product during the thermal process using a hot plate. Thus, firstly, a denser product B, and thus a product with fewer pores, is obtained, showing a decrease in both thermal conductivity and acoustic properties.
<< Aspect 1 >>
A composite molded product comprising at least one polyamide reinforced layer comprising a polyamide matrix and reinforcing fibers, wherein the polyamide reinforced layer is a pressurized steam process between the matrix material in the form of fibers or powder or flakes and the reinforcing fibers Molded product characterized by being porous due to integration using
<< Aspect 2 >>
A molded product according to aspect 1, wherein the reinforcing fibers are selected such that the dynamic Young's modulus of the polyamide reinforcing layer does not change more than 20% over the temperature range of 150C to 210C.
<< Aspect 3 >>
The molded product according to aspect 1 or 2, wherein the density of the composite material is 5 to 80% of the bulk density of the material of the polyamide reinforcing layer.
<< Aspect 4 >>
The molded product according to any one of aspects 1 to 3, wherein the final product has a tensile loss coefficient (-) of less than 0.15 over a temperature range of 60C to 210C.
<< Aspect 5 >>
A product according to any one of embodiments 1 to 4, wherein the polyamide matrix is polyamide-6 or polyamide-6.6 or a mixture of different types of polyamides.
<< Aspect 6 >>
The molded product according to any one of aspects 1 to 5, wherein the reinforcing fiber is a mineral fiber such as glass fiber, carbon fiber, or basalt fiber.
<< Aspect 7 >>
The molded product according to any one of aspects 1 to 5, wherein the reinforcing fiber is a thermoplastic polymer fiber having a melting temperature measured by DSC that is higher than the melting temperature of the polyamide under vapor pressure.
<< Aspect 8 >>
Production of a porous molded product comprising randomly placed polyamide bonded fibers or flakes or powders and reinforcing fibers forming a web and treating the web with pressurized steam to solidify the web Method.
<< Aspect 9 >>
Process according to embodiment 8, wherein saturated steam in the range of 9 to 20 bar absolute pressure is used.
<< Aspect 10 >>
10. A method according to aspect 8 or 9, wherein the web is treated in a pressure resistant mold having at least one vapor permeable surface to form a molded product.
<< Aspect 11 >>
11. A method according to any one of aspects 8 to 10, wherein the web is pre-bonded, preferably by needling, before being transferred to steam treatment.

Claims (11)

A composite molded product for automobile panel comprising at least one polyamide reinforcing layer made of a polyamide matrix and reinforcing fibers, the polyamide reinforcing layer, and the matrix material in the form of fibers or powder or flakes, wherein the reinforcing fibers Molded product for automobile panel , characterized in that it is porous due to integration using a pressurized steam process. The reinforcing fibers, dynamic Young's modulus of the polyamide reinforcing layer over a temperature range of 0.99 ° C. to 210 ° C., is selected as many than 20% unchanged, molded product according to claim 1.   The molded product according to claim 1 or 2, wherein the final product has a tensile loss factor (-) of less than 0.15 over a temperature range of 60C to 210C. 4. Product according to any one of claims 1 to 3, wherein the polyamide matrix is polyamide-6 or polyamide-6.6 or a mixture of different types of polyamides. It said reinforcing fibers are mineral fibers, molded product according to any one of claims 1 to 4. It said reinforcing fibers is higher than the melting temperature of the polyamide in the vapor pressure is a thermoplastic polymer fibers having a melting temperature measured by DSC, molded product according to any one of claims 1 to 4. Porous for automotive panels comprising randomly placed polyamide bonded fibers or flakes or powders and reinforcing fibers forming a web and treating the web with pressurized steam to integrate the web Manufacturing method of quality molded products.   8. Process according to claim 7, wherein saturated steam in the range of 9 to 20 bar absolute pressure is used.   9. A method according to claim 7 or 8, wherein the web is processed in a pressure resistant mold having at least one vapor permeable surface to form a molded product.   10. A method according to any one of claims 7 to 9, wherein the web is pre-bonded before being transferred to steam treatment.   The method of claim 10, wherein the web is pre-bonded by needling before being transferred to steam treatment.

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